Welcome to the Community, nur_syafiqah95.
Let me share some insights about custom fields in QuickBooks Desktop.
You can create and use custom fields for customers, suppliers, employees, and items in QuickBooks Desktop. However, an option to add a custom field for cheques is currently unavailable.
Alternatively, you can use the Memo field to add the payment voucher reference number.
I've added this link to learn how you can create, modify, and print cheques in QuickBooks Desktop.
Just drop a comment below if you have other concerns about cheques. I'll be glad to help. Take care and have a great day!